Transporting Mares and Foals

Transporting Mares and Foals

Make certain that the foal (as well as the mare) has been taught to load and unload from a trailer.

Photo: Anne M. Eberhardt/The Horse

Transporting a horse is always fraught with potential problems. The potential for trouble increases when a foal, only weeks (or days) of age, is added into the mix, such as at breeding time when a mare must travel away from her home farm. In some cases, the transportation is only down the road a short distance to the breeding barn. In other instances, it might be all the way across the country.

Thanks to artificial insemination, it is not always necessary to transport a mare and foal to the stallion's resident farm for breeding. Instead, semen is shipped to the mare's owner for use at home. However, if the mare involved is a Thoroughbred, that is not an option since only live cover is allowed by the breed registry. There are also instances where a stallion's semen doesn't tolerate the shipping process. For some reason, the semen deteriorates rapidly when cooled, placed in a container, and sent across the country. In still other instances, the owner of a popular stallion simply might not want to go through the effort of collecting and sending semen. If you want to breed to him, you must send the mare. It is as simple as that.

Regarding the effects of transportation on foals, we generally have to start with research on adult horses. The University of California, Davis (UC Davis), reported on some extensive studies conducted by the team of Carolyn Stull, MS, PhD, from the UC Davis Center for Equine Health; and Ann Rodiek, MS, PhD, from California State University in Fresno. They studied the physiology of horses both during transport and during recovery. The study was conducted using a commercial equine van that traveled the interstate highways of central California under typical summer conditions.

The horses studied included 15 mature, healthy animals which were experienced travelers. Their physiological responses were documented during 24 hours of road transport, followed by a 24-hour recovery period during which horses rested in individual stalls. The findings of that study were reported in the October 2003 issue of The Horse Report  (online at, a publication detailing research findings at the University of California, Davis.

Factors in the transport that contribute to stress, they found, include those that are physical--such as confinement, withholding of food and/or water, trailer motion, noise, and road conditions. Psychological stressors included separation from the herd and exposure to unfamiliar environments, including air temperature.

We will first pass along the researchers' findings, since this is the most current information available, then offer some tried and true tips for transporting mares and foals. When looking at the UC Davis report, one thing is immediately obvious: The horses being dealt with are adults, not foals. The problem, says Stull, is that very little research has been carried out on the transportation of foals, so there is little in the literature. We can only assume that the stresses suffered by adult horses would be compounded in a mare with a nursing foal at her side. Stull feels that the same is true for foals. In the absence of scientific evidence, she believes the factors that weigh on adult horses will weigh even more heavily on foals because they are less experienced in the environment compared to adults, and they have immature immune systems.

Research Findings

One of the goals of the UC Davis research was to learn how quickly physiological responses returned to baseline or pre-travel levels following a long trailer or van ride.

The researchers outlined their findings in four categories--general health, dehydration, muscle fatigue, and stress.

General Health--The horses lost about 6% of their body weight during 24 hours of road transport. The loss, the researchers concluded, was likely due to heat dissipation, sweat loss, and decreased gut fill while traveling. The good news is that the horses recovered at least half of their weight loss within 24 hours of disembarking from the van. The fact that horses lost weight and regained half of it within 24 hours, the researchers indicate, might support the notion that horses respond to heat stress during transit through respiration and sweating mechanisms. In addition to measuring body weight, white blood cell counts also were measured as general indications of health, and they demonstrated a compromised immune system associated with transport (more on this in a moment).

Dehydration--The report had this to say concerning dehydration: "Hematocrit (relative volume of blood with oxygen-carrying cells, or red blood cells) and total protein concentrations are often used as indicators of dehydration in horses. These measurements also showed differences (increases) during transit, with a return to baseline values during the post-transit period, indicating some dehydration had occurred. Interestingly, during the last 12 hours of transport when the hematocrit levels peaked, the horses had consumed 91% of the water offered."

Muscle Fatigue--The study indicated that the horses involved suffered little from muscle fatigue. However, the report did note that two serum enzymes with high activity in skeletal muscle that are evaluated clinically in horses with muscular diseases--creatine phosphokinase (CPK) and aspartate animotransferase (AST)--were elevated during transportation. CPK, they note, was slightly elevated after travel, and AST rose in response to transport and returned to baseline within 24 hours after transport. This means that there is some mild muscle damage during transport. Horses in trailers use their muscles constantly to adapt to the situation and stay upright. Owners should allow their horses time for recovery after trailering long distances before working with the horses.

Stress--Stress is capable of compromising the immune system. Here is what the report said: "During stressful situations such as exercise or transport, activation of the hypothalamic-pituitary-adrenal axis results in an increased concentration of the hormone cortisol in blood circulation. The concentration of cortisol in these horses increased during loading and continued to rise throughout the 24-hour transit period, peaking at the termination of transit. After unloading, the stress of transportation ceased and cortisol concentration dramatically decreased. This large increase of cortisol during transport influences the immune system, and its influence can be measured by the ratio of two types of white blood cells, namely the neutrophil:lymphocyte (N:L) ratio. This ratio also increased during transit and did not return to baseline within the 24-hour recovery period. This continued elevation in the N:L ratio may contribute to disease susceptibility following long-term transport.

"Horses in this study that underwent 24 hours of transport in hot summer conditions clearly showed physical responses that included changes in stress measures, serum metabolites, dehydration and immune indicators, body weight, and rectal temperatures," said the report.

Confinement During Travel

The way in which horses were confined during transport in the study had a profound effect on the amount of stress from which they appeared to suffer. The least desirable confinement, the researchers report, was cross-tying. The most advantageous situation for horses' health was to be loose in a small box stall-like compartment. This is the recommended way to ship mares with foals at their side.

Overall, the researchers found, the cross-tied horses had larger increases of selected stress parameters following transport than did horses traveling without being tied. A substantial increase in the aforementioned N:L ratio, they say, was seen in the cross-tied horses when compared with the loose horses.

Other studies, they report, have found that elevation of the horse's head--which restricts the range of neck movement--compromises the immune system and increases the number of bacteria in transtracheal aspirates (fluid samples collected from the horse's airways). The increase in bacteria is thought to be the result of a decrease in clearance rate of the bacteria from the tracheobronchial secretions in horses which are confined and unable to lower their heads. Thus, they reason, tying horses in this manner for long trips might predispose them to respiratory disorders, particularly pleuritis or "shipping fever."

And, we must conclude, if this is the case for adult horses, it will be true for foals. The UC Davis study and other similar studies have produced milestones in transportation research.

Making Shipping Easier on Horses

In the wake of their findings, the researchers offered recommendations for minimizing the stress of transport:

  • Start with a healthy horse. Horses with subclinical or clinical respiratory disease should avoid transport except in emergency situations. Consult a veterinarian with these cases prior to shipping.
  • During long-term transport (greater than six to eight hours), do not elevate or restrict the movement of the head and neck by cross-tying. A small box stall that allows the horse to drop his head is preferred for minimizing stress and susceptibility to disease after transport.
  • Dietary adjustments are not necessary in horses shipped short distances. However, horses intended to endure long transportation schedules should be provided with feed and water on a regular schedule. Laxatives, such as bran mashes, might not be necessary. Some nervous horses might develop loose manure or diarrhea and become dehydrated from the loss of fluids.
  • If you provide hay to your horse during transport, make sure it is quality hay with minimal dust and mold.
  • Water should be offered every six to eight hours if possible. Allow the horse to drink his fill. However, many horses might not drink water during transit. Therefore, you might want to carry water from home or begin flavoring water at home until the horse is used to it, and then flavor water from the new location to increase intake.
  • Relative humidity and environmental temperature rise quickly in stationary closed vehicles. Horses should be unloaded upon arrival or during stops to minimize thermal (heat) stress, especially during summer.
  • Respiratory ailments, such as shipping fever and pneumonia, might not cause clinical signs for two to three days following transport. However, depression in the attitude of the horse, lack of appetite, and the development of coughing or nasal discharge might be signs of shipping fever. Death within 30 days following transport due to pneumonia has been reported in horses transported over durations of eight to 43 hours. Daily recording of rectal temperatures is advisable. A veterinarian should be consulted for horses exhibiting any of these signs.

Tips for Hauling Healthy Horses

Now for some time-tested basic tips from a number of veterinarians and veteran horse haulers, as well as from Stull, to add to the suggestions already offered by the UC Davis researchers.

  • Make certain the foal has been halter-broken before heading to the breeding farm. It might be necessary to unload the horses en route, and a free-running foal can possibly injure himself, either at that location or upon arrival at the breeding station.
  • Make certain that the foal (as well as the mare) has been taught to load and unload from a trailer. The trip will be stressful enough. Battling the foal into the trailer, while the dam gets agitated as well, only adds to the stress. The more a foal is handled in the first days and weeks of life, the better. If a foal isn't handled before transportation, you likely will be dealing with a frightened, skittish youngster which could injure himself in the trailer.
  • Make sure the trailer is spacious enough so the mare and foal can be free in a box stall setting. If the mare is overly agitated, tie her for the first few miles until she settles down.
  • Bed the trailer with shavings that are fresh and not dusty.
  • Make certain the trailer has adequate ventilation.
  • Make certain the truck and trailer are in good working order.
  • Stop frequently when transporting a mare and foal. A foal often will lie down in the shavings and rest while traveling. Frequent stops will allow him to rise and nurse without being bounced about.
  • Offer the mare water frequently. Remember that she is still producing milk and needs the liquid. If she refuses to drink, there is little you can do about it on the road. It might be helpful to carry water from home so that the taste is familiar to her.
  • If you break the trip into two segments, you should either have a predetermined place to stop and unload horses in a safe area, or be prepared to turn the entire trailer into a box stall for the night.
  • If you are unable to find a suitable layover spot where you can unload, it might be necessary to keep traveling, but with suitable rest stops for watering and feeding in the trailer to avoid heat buildup inside.
  • Upon arrival, insist that the breeding farm keep a close watch on both mare and foal to monitor their recovery from the stress of travel. (Most breeding farms will do this routinely as they normally quarantine new arrivals to prevent the spread of disease on the premises.)

Traveling with a mare and foal sometimes is a necessary evil, but if one follows the suggestions of the UC Davis researchers as well as those from veterinarians and horsemen, most problems can be avoided.

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

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